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### Constructing an Offset Line

You can construct an offset line between the input features and then offset by specified distances from the input features.

To construct an offset line:

1. Access the Construct Line dialog box (Insert | Feature | Constructed | Line).

2. Select the Offset option.

3. Select at least two features from which to create the offset line. They can be of any type.

4. Click the Offsets button. The Line Offsets dialog box appears.

Line Offsets dialog box

5. Choose either to calculate the nominals from the offsets or calculate the offset value from the specified nominal values.

- To calculate the nominals from the offset values, select the Calculate nominals option. In the Offset field, type the offset values for the desired features and then click Calculate.

- To calculate the offsets, select the Calculate offsets option, modify the nominal values, and then click Calculate. For more information, see the procedures below.

6. Click the OK button to close the Line Offsets dialog box.

7. Click the Create button to create the constructed offset line based on your values.

If the offset values exceed the distance between the input features, Planner cannot solve the offset line. Instead, it constructs a line without any offsets between the first and last feature.

How It Works

Consider these statements along with the pictures below:

- Planner makes all offsets in a direction perpendicular to the given surface normal direction.

- Planner attempts to construct the line starting at the first input feature and ending at the last input feature.

- An offset value basically results in an imaginary circle drawn around each input feature's centroid by that value.

- Planner attempts to construct a line tangent to the imaginary circle around each input feature's offset radius. A tangent line touches the circle at only one point.

- In cases where more than two input features are used and they have varying offset values, Planner cannot construct a line tangent to all the offsets; instead, it tries to accommodate the offsets as best it can with a best fit line.

- Planner constructs a line so that the shortest distance from each input feature to the line is the corresponding offset amount.

- The offsets signs are determined by the direction of the line.

Suppose you have two points as input features, and the second point has an offset value:

1. First point

2. Second point

3. Resulting line if no offset is defined

4. Offset distance (radius) from the feature's center that results in an imaginary circle around the feature

5. Constructed line from starting feature tangent to the imaginary circle

For example, suppose you have four points as your input features, and each point has a different offset value, as indicated by their circles. Planner constructs a best fit line that is tangent to those circles, as indicated in this diagram:

A positive or negative value on the offset determines on what side of the circle the line is constructed. For example, suppose you reverse the signs on all the offsets, from positive to negative, you might end up with something similar to this:

If you get a line opposite from what you expected, cancel the feature and reconstruct it, and try reversing the sign of the offsets values.

Examples

Here are some examples:

Example 1 - F1 and F2 are the inputs. Both have offsets that are set to zero:

Example 2 - F1 and F2 are the inputs. The F1 offset is set to 0. The F2 offset is set to 25:

Example 3 - F1 and F2 are the inputs. The F1 offset is set to 0. The F2 offset is set to -25:

Example 4 - F1 and F2 are the inputs. Both offsets are set to -25:

More:

Changing Offsets Directly to Calculate Nominals

Example of Calculating Nominals

Changing Nominals Directly to Calculate Offsets

Example of Calculating Offsets